The invention relates to a semiconductor including a lateral HEMT and to a method for production of a semiconductor including a lateral HEMT.
The majority of previous power semiconductor components have been produced based on silicon. Associated with this, the power density which can be achieved and the operating temperature of the semiconductor components are limited. Applications at high frequencies are also reaching their limits. The main reason for this is the limited breakdown field strength of silicon, since, in the end, this governs the thickness of the depletion layer and its maximum doping.
The requirement for ever higher performance with ever lower production costs for power semiconductor components has in the meantime necessitated the miniaturization of the components to such an extent that the power density has reached the physical limits of silicon.
Alternative material systems are often compound semiconductors which have a greater band gap, a higher breakdown field strength and often also better thermal conductivity in comparison to silicon. The best known material for this purpose in the field of power semiconductor components is SiC which, despite known restrictions relating to the wafer size and the material quality as well as the channel mobility, are used in particular for diodes and bipolar transistors in high blocking capability components. Until now, field-controlled components have existed only in the form of JFETs which, however, have the disadvantage that they are depletion-type components. Particularly in high-power application areas, in contrast, enhancement-type components are actually preferred since fault situations can be coped with considerably more easily with them during use. Semiconductors with a large band gap, in particular III-V nitrides, are further material systems which are highly suitable for optical and further electronic semiconductor components, because of their characteristics. In addition to optoelectronics, these material systems are also increasingly being used in radio-frequency technology.
The use of these material systems is also advantageous for the power electronics field since, in comparison to silicon, they allow components with the same blocking capability, with higher doping and a shorter drift zone at the same time. However, the processing of components composed of these material systems is subject to restrictions in comparison to silicon technology, since certain methods which are used in silicon technology are not available, or are available only to a restricted extent, for III-V semiconductor systems.
Power semiconductor components based on III-V compound semiconductors have until now been produced in the form of lateral components. These are so-called HEMTs (high electron mobility transistors), for which one important aspect is the provision of a self-blocking component. In this case, an HEMT has a plurality of layers composed of differently doped semiconductor materials with band gaps of different magnitude. Because the band gaps of the individual layers have different magnitudes, a two-dimensional electron gas (2DEG) is formed at their interface, and acts as a conductive channel. In this case, the electron mobility and the 2D electron charge carrier density in the two-dimensional electron gas are very high.
U.S. Pat. No. 7,250,641 B2 discloses an HFET (heterostructure field effect transistor) based on the material system AlGaN/GaN, in which a two-dimensional electron gas is formed in the interface layer between the two materials. In this case, a layer composed of AlGaN is arranged on a layer composed of GaN. Furthermore, in one embodiment, a p-conductive layer composed of GaN is arranged between the layer composed of GaN and a silicon substrate. This results in a pin diode being formed between the substrate and a drain electrode, as a result of which holes which are generated when an avalanche breakdown occurs are discharged into the substrate via the p-conductive GaN layer.
For these and other reasons there is a need for the present invention.